1. Field of the Invention
This invention is directed to a dedicated dimming system applicable for use with solid state illumination sources, such as LED technology, which provides proper and accurate control of a dimming operation therefor. The system is structured to be easily retrofitted for use with previously installed or existing dimmer systems for incandescent illumination sources. Moreover, whether or not installed as a retrofit, the dimmer system of the present invention is operative to distinguish an intended manual control of a dimming operation of the LED light source, from a non-manual event including a power anomaly in the power supplied to the LED light source.
2. Description of the Related Art
As is recognized, phase control dimmers “chop” an AC waveform to reduce power to light loads, thereby causing a diminishing of light intensity or a “dimming” of a light source. The chop or distortion of the AC waveform essentially comprises a portion of the AC waveform being removed for a period of time of each AC cycle (180 degrees). Accordingly, known phase control dimmers work best with incandescent lamps that present a resistive load to the dimmer. In contrast, light emitting diode (LED) drivers present a reactive load to the dimmer. This means that the LED driver will distort the AC current and voltage significantly by drawing non-linear currents while operating. They also present a zero load condition to the dimmer each AC cycle. Such a zero load condition causes dimmer operation to misfire resulting in a “flicker” or noted visual fluctuation in the intensity of illumination generated. As a result, dimming LED lights with electronic drivers associated with technology designed to drive incandescent bulbs is problematic.
Further factors affecting accurate and reliable operation of LED dimmer assemblies include the fact that power quality in many buildings or other facilities is deteriorating. This is at least partially due to the proliferation of AC/DC power supplies for electronic equipment. Such equipment includes, but is not limited to, computers, telephone equipment, copy machines, fax machines and essentially any device that requires DC voltage to operate, but is fed by AC voltage in the building. Switching power supplies are typically not “power factor corrected” and as such draw their charging current at the peak of the incoming AC waveform. This results in a “flattening” of the waveform because high peak currents cause resistive voltage loss in the building's wiring and transformer cores. Further, the reactive loads from motors and some lighting facilities contribute to the distortion of the AC waveforms. The poor power quality causes LED drivers to misfire and create the “flicker” in the LED currents.
Accordingly, there is a need in this area for a dedicated dimmer solution to be applied for use with solid state illumination sources, including LED lighting technology. Such a preferred system and attendant solution will provide proper and accurate control with minimal risk of misfire. Moreover, a preferred and proposed system for dimming solid state illumination sources can compensate for less than ideal power quality conditions and/or disruptive power supplies.